Banks actually do that though. Credit cards have massive risk analysis engines behind them, and the limits are tied to your creditworthyness. So maybe it's not a good analogy.
Thats for giving you credit. Not for spending your own balance.
It's about spending your balance too. They will block transactions if they think there's a high risk of the transaction triggering a chargeback complaint, if they think the recipient might be sanctioned, if they aren't sure if the card was cloned etc.